driver core: add helper for deferred probe reason setting

We now have three places within the same file doing the same operation
of freeing this pointer and setting it anew. A helper makes this
arguably easier to read, so add one.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.kernel.org/r/20210323153714.25120-2-a.fatoum@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>